Investigation of turbulence modulation in solid–liquid suspensions using parallel competing reactions as probes for micro-mixing efficiency

•The effects of solids on turbulence modulation have been investigated.•Both Bourne and Villermaux scheme show similar effects.•Micro-mixing experiments confirm and extend previous results using PIV.•Smaller particles (70–100 and 250–300μm) gave maximum suppression at ∼1vol%. The Bourne and the Vill...

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Bibliographic Details
Published in:Chemical engineering research & design 2013-11, Vol.91 (11), p.2179-2189
Main Authors: Unadkat, H., Nagy, Z.K., Rielly, C.D.
Format: Article
Language:English
Subjects:
Bourne kinetics
Byproducts
Chemical engineering
Dissipation
Fluid dynamics
Fluid flow
Micro-mixing
Modulation
Multiphase flows
Parallel reactions
Stirred tanks
Turbulence
Turbulent flow
Villermaux kinetics
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Summary:•The effects of solids on turbulence modulation have been investigated.•Both Bourne and Villermaux scheme show similar effects.•Micro-mixing experiments confirm and extend previous results using PIV.•Smaller particles (70–100 and 250–300μm) gave maximum suppression at ∼1vol%. The Bourne and the Villermaux competitive reaction chemistries were applied to study the effects of suspended particles on the yield of an undesired product and hence to infer their effects on local dissipation rates. Two-phase micro-mixing experiments were carried out in a 1l stirred vessel, agitated by a pitched-blade turbine, using four particle size ranges: 70–100, 250–300, 700–750 and 1000μm. Experiments were carried out with up to 1.75vol% particles in the Bourne scheme and 3vol% in the Villermaux scheme. Both reaction schemes gave qualitatively similar results, although stronger effects of added particles were obtained with the Bourne chemistry. The effect of 700–750μm particles could not be distinguished from experimental error, but the other size ranges gave increased by-product yields and suppressed the dissipation rates. These results confirmed earlier two-phase PIV observations: smaller particles (70–100 and 250–300μm) gave maximum suppression at ∼1vol%. Above this volume fraction, the level of suppression decreased and in some cases turbulence augmentation occurred, indicating that particle concentration, as well as size, is an important factor.
ISSN:0263-8762
DOI:10.1016/j.cherd.2013.05.005